Apparatus and methods for manipulating radio frequency power at an edge ring in plasma process device

ABSTRACT

The present disclosure relates to apparatus and methods that manipulate the amplitude and phase of the voltage or current of an edge ring. The apparatus includes an electrostatic chuck having a chucking electrode embedded therein for chucking a substrate to the electrostatic chuck. The apparatus further includes a baseplate underneath the substrate to feed RF power to the substrate. The apparatus further includes an edge ring disposed over the electrostatic chuck. The apparatus further includes an edge ring electrode located underneath the edge ring. The apparatus further includes a radio frequency (RF) circuit including a first variable capacitor coupled to the edge ring electrode.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims benefit of U.S. Provisional Patent ApplicationSer. No. 62/530,774, filed Jul. 10, 2017, and U.S. Provisional PatentApplication Ser. No. 62/669,739, filed May 10, 2018, which applicationsare hereby incorporated by reference herein.

BACKGROUND Field

Examples of the present disclosure generally relate to a plasmaprocessing chamber, and more particularly, to an apparatus and methodsfor manipulating radio frequency (RF) power at an edge ring to controlthe plasma sheath in the plasma processing chamber.

Description of the Related Art

An edge ring is a circular component which surrounds a perimeter of asubstrate, such as a semiconductor substrate, during plasma processingin a process chamber. Due to exposure of the edge ring to plasma withinthe process chamber, the edge ring may erode and require replacement ormaintenance after a predetermined interval. When the edge ring isseverely eroded, the shape of the plasma sheath at the edge of thesubstrate distorts and changes the plasma processing characteristics atthe edge of the substrate. The change in plasma processingcharacteristics causes undesirable processing effects at the edge of thesubstrate, thus reducing the usable yield near the edge of thesubstrate. Other methods and apparatus for controlling a plasma sheathexist, such as edge rings which are movable relative to the substrate.However, certain electronic device manufacturing processes are subjectto stringent particle requirements which make moving parts undesirable.

Therefore, there is a need for apparatus and methods that address edgering erosion to improve the process uniformity on a substrate.

SUMMARY

The present disclosure provides apparatus and methods for manipulatingthe voltage at the edge ring, which can perform as an effective tuningknob to control the process profile near a substrate edge. Manipulatingthe edge ring's voltage can improve the process uniformity on asubstrate. Also, controlling the edge ring's voltage can assist incontrolling the verticality (i.e., tilting) of features formed near thesubstrate edge.

In one aspect, the apparatus includes an electrostatic chuck having achucking electrode embedded therein for chucking a substrate to theelectrostatic chuck. The apparatus further includes a baseplateunderneath the substrate to feed RF power to the substrate. RF power canalso be fed to the substrate using the chucking electrode. The apparatusfurther includes an edge ring disposed around the electrostatic chuck.The apparatus further includes an edge ring electrode located underneaththe edge ring. The apparatus further includes a radio frequency (RF)circuit including a first variable capacitor coupled to the edge ringelectrode.

In another aspect, the apparatus includes a process chamber thatincludes a chamber body, a lid disposed on the chamber body, aninductively coupled plasma apparatus positioned above the lid, and asubstrate support positioned within the chamber body. The substratesupport includes an electrostatic chuck having a chucking electrodeembedded therein. The substrate support further includes a baseplateunderneath the chucking electrode to feed RF power to the substrate. Thesubstrate support further includes an edge ring electrode located abouta periphery of the baseplate. The process chamber further includes aradio frequency (RF) circuit comprising a first variable capacitor, afirst inductor, and a second inductor coupled to the edge ringelectrode.

In another aspect, a method of operating a process chamber comprisesmonitoring an amplitude ratio and phase difference between voltages ofan edge ring and a substrate by monitoring an amplitude ratio and phasedifference between the voltages of an edge ring electrode and a chuckingelectrode. The method further includes adjusting an RF power source suchthat the chucking electrode maintains a constant amplitude of voltage byadjusting a radio frequency (RF) circuit including at least one variablecapacitor coupled to the edge ring electrode. The method furtherincludes tuning the at least one variable capacitor to obtain a targetamplitude of the voltage at the edge ring.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the presentdisclosure can be understood in detail, a more particular description ofthe disclosure, briefly summarized above, may be had by reference toembodiments, some of which are illustrated in the appended drawings. Itis to be noted, however, that the appended drawings illustrate onlyexemplary embodiments and are therefore not to be considered limiting ofits scope, and may admit to other equally effective embodiments.

FIG. 1 is a schematic sectional view of a process chamber according toone embodiment of the disclosure.

FIGS. 2A and 2B illustrate enlarged schematic views of the substratesupport shown in FIG. 1.

FIGS. 3A-3C are schematic views of a plasma sheath relative to theperimeter of a substrate, according to embodiments of the disclosure.

FIGS. 4A and 4B illustrate schematic circuit diagrams illustrating oneembodiment of a RF circuit.

FIGS. 5A and 5B illustrate schematic circuit diagrams illustrating oneembodiment of a RF circuit.

FIGS. 6A and 6B illustrate schematic circuit diagrams illustrating oneembodiment of a RF circuit.

FIGS. 7A and 7B illustrate schematic circuit diagrams illustrating oneembodiment of a RF circuit.

FIGS. 8A and 8B illustrate schematic circuit diagrams illustrating oneembodiment of a RF circuit.

FIGS. 9A and 9B illustrate schematic circuit diagrams illustrating oneembodiment of a RF circuit.

FIGS. 10A and 10B illustrate schematic circuit diagrams illustrating oneembodiment of a RF circuit.

FIGS. 11A and 11B illustrate schematic circuit diagrams illustrating oneembodiment of a RF circuit.

FIG. 12A and 12B illustrate schematic circuit diagrams illustrating oneembodiment of a RF circuit.

FIG. 13A and 13B illustrate schematic circuit diagrams illustrating oneembodiment of a RF circuit.

FIG. 14A and 14B illustrate schematic circuit diagrams illustrating oneembodiment of a RF circuit.

FIG. 15A and 15B illustrate schematic circuit diagrams illustrating oneembodiment of a RF circuit.

FIG. 16 is a schematic side view illustrating a portion of a substratesupport assembly having a quartz cover ring disposed on the edge ring.

FIG. 17 is a flow diagram illustrating an operation process for the RFcircuits according to one aspect of the disclosure.

FIG. 18 is a flow diagram illustrating an operation process for the RFcircuits according to another aspect of the disclosure.

FIGS. 19A to 19D show simulation results of the amplitude ratio and thephase difference between the edge ring electrode and the substrateelectrode according to one aspect of the disclosure.

To facilitate understanding, identical reference numerals have beenused, where possible, to designate identical elements that are common tothe figures. It is contemplated that elements and features of oneembodiment may be beneficially incorporated in other embodiments withoutfurther recitation.

DETAILED DESCRIPTION

The present disclosure generally relates to apparatus and methods thatcontrol radio frequency (RF) amplitude and phase of a substrate supportassembly. The apparatus and methods include an electrode that is coupledto ground through a variable capacitor and optionally an inductor. Theelectrode may be ring-shaped and embedded in a substrate support thatincludes an electrostatic chuck. The electrode may be positioned beneaththe perimeter of a substrate and/or an edge ring positioned on aperimeter of the substrate support. As the plasma sheath drops adjacentthe edge ring due to edge ring erosion, the capacitance of the variablecapacitor is adjusted in order to affect the RF amplitude near the edgeof the substrate. Adjustment of the RF amplitude via the electrode andvariable capacitor results in an adjustment of the plasma sheath nearthe substrate perimeter. Bending of the sheath at the perimeter of thesubstrate will either focus ions (increase etch rate) or de-focus ions(decrease etch rate) in the region of approximately 0 mm-10 mm(depending on the process condition) from the edge of the substrate.

The present disclosure also addresses the need to compensate for extremeedge non-uniformities left by previous process steps. In all of theseapplications, when the process is very sensitive to particles, forexample in logic circuit applications, it is considered a high risk tohave moving parts in the vicinity of the substrate. The presentdisclosure addresses the need for extreme edge RF tunability with nomoving parts.

FIG. 1 is a schematic sectional view of a process chamber 100, accordingto one example of the disclosure. The process chamber 100 includes achamber body 101 and a lid 102 disposed thereon that together define aninner volume. The chamber body 101 is typically coupled to an electricalground 103. A substrate support assembly 104 is disposed within theinner volume to support a substrate 105 thereon during processing. Anedge ring 106 is positioned around the periphery of the substrate 105 onthe substrate support assembly 104. The process chamber 100 alsoincludes an inductively coupled plasma apparatus 107 for generating aplasma of reactive species within the process chamber 100, and acontroller 108 adapted to control systems and subsystems of the processchamber 100.

The substrate support assembly 104 includes one or more electrodes, suchas a first electrode 109 and a second electrode, such as an edge ringelectrode 111 are coupled to a RF power source 110 (at a first frequencyand, in some embodiments, alternatively to a second RF power source 170at a second frequency. Unless otherwise noted, hereinafter “the RF powersource 110”) through a matching network 112 and a tuning circuit 155including variable capacitors and inductors. The RF power source 110 isutilized to bias the substrate 105 disposed on an upper surface 160 ofthe substrate support assembly 104. The RF power source 110 mayillustratively be a source of up to about 1,000 W (but not limited toabout 1,000 W) of RF energy, which may be provided by one or multiplefrequencies, such as 13.56 MHz and 2 MHz. In another embodiment, the RFpower source 110 may be two separate power sources with differentfrequencies, e.g., 2 MHz and 13.56 MHz, which can be used separately ortogether. The RF power source 110 may be capable of producing either orboth of continuous or pulsed power. The first electrode 109 is coupledto a chucking power source 114 to facilitate chucking of the substrate105 to the upper surface 160 during processing. The bias RF source 110can be delivered to the substrate 105 either through coupling to thebaseplate 210 or connecting to the substrate electrode 109.

The inductively coupled plasma apparatus 107 is disposed above the lid102 and is configured to inductively couple RF power into the processchamber 100 to generate a plasma 116 within the process chamber 100. Theinductively coupled plasma apparatus 107 includes first and second coils118, 120, disposed above the lid 102. The relative position, ratio ofdiameters of each coil 118, 120, and/or the number of turns in each coil118, 120 can each be adjusted as desired to control the profile ordensity of the plasma 116 being formed. Each of the first and secondcoils 118, 120 is coupled to an RF power supply 110 through a matchingnetwork 122 via an RF feed structure 124. The RF power supply 110 mayillustratively be capable of producing up to about 4000 W (but notlimited to about 4000 W) at a tunable frequency in a range from 50 kHzto 13.56 MHz, although other frequencies and powers may be utilized asdesired for particular applications.

In some examples, a power divider 126, such as a dividing capacitor, maybe provided between the RF feed structure 124 and the RF power supply121 to control the relative quantity of RF power provided to therespective first and second coils 118, 120. In some examples, the powerdivider 126 may be incorporated into the matching network 122.

A heater element 128 may be disposed on the lid 102 to facilitateheating the interior of the process chamber 100. The heater element 128may be disposed between the lid 102 and the first and second coils 118,120. In some examples, the heater element 128 may include a resistiveheating element and may be coupled to a power supply 130, such as an ACpower supply, configured to provide sufficient energy to control thetemperature of the heater element 128 within a desired range.

During operation, the substrate 105, such as a semiconductor wafer orother substrate suitable for plasma processing, is placed on thesubstrate support assembly 104. Substrate lift pins 146 are movablydisposed in the substrate support assembly 104 to assist in transfer ofthe substrate 105 onto the substrate support assembly 104. Afterpositioning of the substrate 105, process gases are supplied from a gaspanel 132 through entry ports 134 into the inner volume of the chamberbody 101. The process gases are ignited into a plasma 116 in the processchamber 100 by applying power from the RF power supply 121 to the firstand second coils 118, 120. In some examples, power from the RF powersource 110, such as an RF or a pulsed DC source, may also be providedthrough the matching network 112 to electrodes 109 within the substratesupport assembly 104. The pressure within the interior of the processchamber 100 may be controlled using a valve 136 and a vacuum pump 138.The temperature of the chamber body 101 may be controlled usingfluid-containing conduits (not shown) that run through the chamber body101.

The process chamber 100 includes the controller 108 to control theoperation of the process chamber 100 during processing. The controller108 comprises a central processing unit (CPU) 140, a memory 142, andsupport circuits 144 for the CPU 140 and facilitates control of thecomponents of the process chamber 100. The controller 108 may be one ofany form of general-purpose computer processor that can be used in anindustrial setting for controlling various chambers and sub-processors.The memory 142 stores software (source or object code) that may beexecuted or invoked to control the operation of the process chamber 100in the manner described herein.

During processing, an upper surface 150 of the edge ring 106 may becomeeroded. The erosion changes the plasma characteristics which may alterthe plasma 116 at or near the edge of the substrate 105. In oneembodiment, the software of the memory 142 comprises the instructionsfor manipulating various RF circuits provided in this disclosure toobtain a target amplitude and phase of the voltage at the edge ring 106in order to tune the process profile and/or feature tilting on the edgeof the substrate 105.

FIGS. 2A and 2B illustrate enlarged schematic views of the substratesupport assembly 104 shown in FIG. 1. The substrate support assembly 104includes a ground plate 200 surrounding an insulating layer 205, afacilities plate 210, and an electrostatic chuck 215 assembled in avertical stack. A quartz pipe ring 220 circumscribes the facilitiesplate 210 and the electrostatic chuck 215 to insulate the RF-hotelectrostatic chuck 215 from the ground plate 200. A plasma shield 225is disposed on an upper surface of the quartz pipe ring 220 tofacilitate plasma containment in the process chamber 100 (shown in FIG.1). A quartz ring 230 is positioned on an upper surface of the plasmashield 225.

The facilities plate 210 is positioned between a lower portion of theground plate 200 and the electrostatic chuck 215. The electrostaticchuck 215 includes a one or more channels 235 formed in a first material236 through which a fluid is provided to facilitate temperature controlof the substrate support assembly 104. The first material 236 is ametallic material, such as aluminum. The electrostatic chuck 215includes the first electrode 109 embedded in a second material 240. Thesecond material 240 is a dielectric material, such as a ceramicmaterial, for example, alumina or aluminum nitride. A heater 245 isdisposed adjacent to or in the electrostatic chuck 215 to facilitatetemperature control of the substrate 105. The heater 245 may be, forexample, a resistive heater having a plurality of resistive heatingelements embedded therein.

A ceramic ring 250 surrounds and abuts the radially-outward edges of thesecond material 240. The ceramic ring 250 may be made of, for example,alumina or aluminum nitride.

The edge ring electrode 111 is embedded in the ceramic ring 250. Theedge ring electrode 111 may be positioned about 0.3 millimeters to about1 millimeter from the upper surface of the ceramic ring 250, such asabout 0.75 millimeters. The edge ring electrode 111 may have a width ofabout 3 millimeters to about 20 millimeters, such as about 6millimeters.

The edge ring electrode 111 is positioned radially outward of theperimeter of the substrate 105 and beneath the edge ring 106. In oneexample, the edge ring electrode 111 may have an inner diameter greaterthan 200 millimeters, or greater than 300 millimeters, or greater than400 millimeters. The edge ring electrode 111 is electrically coupled toground and/or match network 112 through the tuning circuit 155consisting of variable capacitors and inductors. The edge ring electrode111 may be coupled to the tuning circuit 155 through multipletransmission lines 265 (two are shown). For example, the edge ringelectrode 111 may be coupled to the tuning circuit 155 through threetransmission lines 265 spaced about the substrate support assembly 104at even intervals (e.g., 120 degrees).

The edge ring 106 is positioned over the ceramic ring 250 and in contactwith the ceramic ring 250 and the second material 240. In one example,the edge ring 106 may be formed from silicon carbide, graphite coatedwith silicon carbide, or low resistivity doped silicon. The edge ring106 circumscribes the substrate 105 and reduces undesired etching ordeposition of material at the radially-outward edges of the substrate105.

Referring to FIG. 2B, during processing, a plasma sheath 260 may formover the surface of the substrate 105 (shown as a dashed line in FIG.2B). As described above, processing conditions may erode the upperportion of the edge ring 106, causing undesired processing of the edgeof the substrate 105, such as rounding, sometimes referred to as a“rollover effect”. The undesired processing reduces device yield andaffects center-to-edge uniformity. To reduce these undesired effects,conventional approaches frequently replaced the edge ring 106. However,frequent replacement of the edge ring 106 is expensive, because itrequires a new edge ring and because replacement of the edge ring 106requires significant down time.

In contrast to conventional approaches, in examples described herein,the edge ring electrode 111 is coupled to ground and/or a RF source 110through the tuning circuit 155 to adjust the RF amplitude and/or phase,and thus the plasma sheath 260, near the edge ring 106.

In another embodiment, a thicker or thinner plasma sheath 260 above theedge ring 106 than that above the substrate 105 is desired in order totune one or a combination of the film etching, deposition profile orfeature tilting angle near the substrate edge. Controlling the voltageamplitude and/or phase of the edge ring 106 relative to those on thesubstrate 105 allows such process edge profile tuning.

Due to the relatively reduced thickness of the ceramic ring 250 incontrast to conventional approaches, RF power initially delivered to theelectrostatic chuck 215 has a high RF coupling with the edge ring 106.In other words, the RF amplitude on the edge ring 106 could be higherthan the RF amplitude on the substrate 105.

In one optional example, a gap 255 may be provided between an uppersurface of the ceramic ring 250 and a lower surface of the edge ring106. The gap 255 may be utilized to decrease coupling between the edgering electrode 111 and the plasma sheath 260 to reduce the RF current totuning circuit 155. The thickness of the gap 255 may be selected toprovide a desired amount of decoupling.

In addition to the examples described above, other examples of thedisclosure are also contemplated. In one example, the length of thetransmission line 265 may have a length that is lambda (wavelength)divided by 2 (e.g., λ/2) to facilitate matched impedance, in at leastone frequency. In another example, it is contemplated that the width ofthe edge ring electrode 111 may be selected to increase or decreaseelectrical coupling with the edge ring 106, as desired. In anotherexample, it is contemplated that the optional gap 255 may be omitted. Inanother example, it is contemplated that a conductive thermal gasket,for example, a silicone-based thermal gasket, may occupy the gap 255.

In another example, the tuning circuit 155 may be coupled to the RFpower source 110 instead of, or in addition to, ground. In such anexample, the tuning circuit 155 would facilitate adjustment ofcapacitive coupling, rather than a parasitic effect as described above.

FIGS. 3A-3C are schematic views of a plasma sheath 260 relative to theedge of a substrate 105, according to examples of the disclosure. FIG.3A illustrates the plasma sheath 260 relative to an edge ring 106 and asubstrate 105 prior to erosion of the edge ring 106.

As illustrated in FIG. 3A, the upper surface of the edge ring 106 andthe substrate 105 are generally coplanar prior to erosion of the edgering 106. Prior to erosion of the edge ring 106, the plasma sheath 260is substantially parallel with and equally spaced from the uppersurfaces of the edge ring 106 and the substrate 105. The profile of theplasma sheath 260 illustrated in FIG. 3A results in uniform processingof the substrate 105, particular near the radially-outward edge thereof.

After processing a predetermined number of substrates, conditions in theprocess chamber result in undesired erosion of the edge ring 106. FIG.3B illustrates an eroded edge ring 106. In one example, the uppersurface of the edge ring 106 may be eroded, thereby reducing thethickness of the edge ring 106. The eroded edge ring 106 no longershares a coplanar upper surface with the substrate 105. Due to theinteraction between edge ring 106 and charged particles in a plasma, theprofile of the plasma sheath 260 is changed in the presence of theeroded edge ring 106.

As illustrated in FIG. 3B, the plasma sheath 260 is changed at theinterface of the substrate 105 and the edge ring 106 and fails tomaintain equidistant spacing between the surface of the edge ring 106and the substrate 105. The profile of the plasma sheath 260 may resultin “rounding” or other undesired processing of the radially-outward edgeof the substrate 105. Rounding at the substrate edge decreases theusable surface of the substrate 105, thus decreasing device yield persubstrate. This undesired rounding may commonly be referred to as the“rollover effect”. In conventional systems, to correct this rounding,the eroded edge ring 106 would be replaced, thus increasing direct costsas well as the cost of lost-production due to processing down time. Incontrast, examples of the present disclosure utilize an edge ringelectrode 111 to adjust the RF amplitude, and then thus the location ofthe plasma sheath 260, above the eroded edge ring 106.

FIG. 3C illustrates the reestablishment of the original (e.g., planar)profile of the plasma sheath 260 after compensating the eroded edge ring106 by means of various RF circuits provided in the present disclosure.

The reestablished plasma sheath 260 does not cause a “rollover effect”on the substrate 105, thus preventing damage to the substrate 105 andmaximizing the usable surface of the substrate 105. Moreover, becausethe eroded edge ring 106 may continue to be utilized in an eroded state,the time between preventative maintenances is extended, therebydecreasing processing downtime. Additionally, the eroded edge ringsrequire less frequent replacement, thereby decreasing expenses forconsumable parts.

FIGS. 4A and 4B are schematic circuit diagrams illustrating oneembodiment of a RF circuit 400. FIGS. 4A and 4B illustrate the RFcircuit 400 within the substrate support assembly 104. To facilitateexplanation, FIG. 4A illustrates the RF circuit 400 overlaid on apartial view of the substrate support assembly 104. The RF circuit 400describes the functional relationships among components of a system. TheRF circuit 400 may be a portion of the tuning circuit 155 shown in FIG.1.

In the RF circuit 400, a capacitance element C1 is present between thebaseplate 405 and an edge ring 106. A capacitance element C2 is presentbetween the edge ring 106 and a plasma 116. A capacitance element C3 isa capacitance between the edge ring 106 and an edge ring electrode 111.A capacitance element C4 is present between the edge ring electrode 111and the baseplate 405. A capacitance element C7 is present between thesubstrate 105 and the plasma 116. A capacitance element C8 is acapacitance between the substrate 105 and baseplate 405. A capacitanceelement C9 is present between the baseplate 405 and the ground.

In one embodiment, the baseplate 405 corresponds to the facilities plate210 (shown in FIGS. 2A and 2B). In another embodiment, a bond layer 410can correspond to the heater 245 (shown in FIGS. 2A and 2B).

In this embodiment, the variable capacitor C5 420 is coupled to the RFpower source 110 and to the edge ring electrode 111 through one or moretransmission lines, providing a path for power to the edge ringelectrode 111. When the power is applied to the edge ring electrode 111,RF voltage and current develop at the edge ring 106 as a result ofcoupling.

In some embodiments, voltages (e.g., V1, V2), currents (e.g., I1, I2),and their phases (e.g., ϕv1, ϕv2, ϕi1, ϕi2) can be measured at the edgering electrode 111 and the baseplate 405. Using the measured voltages,currents, and their phases at these points, the controller 108 monitorsa voltage ratio of edge ring and substrate 105 and a phase differencebetween the voltages of the edge ring 106 and the substrate 105.Additionally or alternatively, the controller 108 monitors a currentamplitude ratio and phase difference between edge ring 106 and substrate105.

Based on the monitoring results, the variable capacitor C5 420 can beadjusted to manipulate voltage or current applied to the edge ringelectrode 111, which affects the voltage or current developed at theedge ring 106. Consequently, the height of the plasma sheath 260 abovethe edge ring 106 can be changed. The total RF power input can be alsoadjusted in order to keep the voltage of the substrate 105 constant forminimal process impact on the center of the substrate 105.

FIGS. 5A and 5B are schematic circuit diagrams illustrating anotherembodiment of a RF circuit 500. FIGS. 5A and 5B illustrate the RFcircuit 500 within the substrate support assembly 104. The RF circuit500 includes the capacitance elements C1, C2, C3, C4, C7, C8 and C9,which are described in the above embodiment illustrated in FIGS. 4A and4B, thus descriptions thereof are omitted.

The RF circuit 500 includes a variable capacitor C5 520 that is coupledto the RF power source 110 and to the edge ring electrode 111 throughone or more transmission lines 141, providing a path for power to theedge ring 106. A variable capacitor C6 530 is also coupled to ground andto a point between the edge ring electrode 111 and variable capacitor C5520.

In some embodiments, voltages (e.g., V1, V2), currents (e.g., I1, I2),and their phases (e.g., ϕv1, ϕv2, ϕi1, ϕi2) can be measured at the edgering electrode 111 and the baseplate 405, respectively. Using themeasured voltages, currents, and their phases at these points, thecontroller 108 monitors a voltage ratio of edge ring 106 and substrate105 and a phase difference between the voltages of the edge ring 106 andthe substrate 105. Additionally or alternatively, the controller 108monitors a current amplitude ratio and phase difference between edgering 106 and substrate 105.

Based on the monitoring results, the variable capacitors C5 520 and C6530 can be tuned to manipulate voltage or current applied to the edgering electrode 111. In one embodiment, the variable capacitor C5 520 canbe used to increase the amplitude of voltage applied to the edge ringelectrode 111, and the variable capacitor C6 530 can be used to decreasethe amplitude of voltage applied to the edge ring electrode 111.Alternatively, C5 520 can decrease the amplitude of voltage applied tothe edge ring electrode 111, and C6 530 can increase the amplitude ofvoltage applied to the edge ring electrode 111.

In another embodiment, the variable capacitor C5 520 can be used toincrease the amplitude of the current applied to the edge ring electrode111. Alternatively, C6 530 can be used to decrease the amplitude of thecurrent applied to the edge ring electrode 111. The total RF power inputcan be also adjusted in order to keep the voltage of the substrate 105constant for minimal process impact on the center of the substrate 105.

FIGS. 6A and 6B are schematic circuit diagrams illustrating anotherembodiment of a RF circuit 600. The RF circuit 600 includes thecapacitance elements C1, C2, C3, C4, C7, C8 and C9, which are describedin the above embodiment illustrated in FIGS. 4A and 4B, thusdescriptions thereof are omitted.

The RF circuit 600 includes a parallel LC resonant circuit coupled tothe ground and to the edge ring electrode 111 through one or moretransmission lines 141. The parallel LC resonant circuit includesvariable capacitor C5 620 and inductor L 630, both coupled to the groundand to the edge ring electrode 111. The controller 108 tunes theparallel LC resonant circuit to manipulate the amplitude and phase ofvoltage or current applied to the edge ring electrode 111 by adjustingthe variable capacitance C5 620.

In some embodiments, voltages (e.g., V1, V2), currents (e.g., I1, I2),and their phases (e.g., ϕv1, ϕv2, ϕi1, ϕi2) can be measured at the edgering electrode 111 and the baseplate 405, respectively. Using themeasured voltages, currents, and their phases at these points, thecontroller 108 monitors a voltage ratio of edge ring 106 and substrate105 and a phase difference between the voltages of the edge ring 106 andthe substrate 105. Additionally or alternatively, the controller 108monitors the current amplitude ratio and the phase difference betweenthe edge ring 106 and the substrate 105. The total RF power input can bealso adjusted in order to keep the voltage of the substrate 105 constantfor minimal process impact on the center of the substrate 105.

In the RF circuit 600, the edge ring electrode 111 functions as a centerof a voltage divider, between voltages of the edge ring 106 andbaseplate 405. As the edge ring 106 is eroded, the parallel LC resonantcircuit increases the amplitude of the voltage or current at the edgering 106 through the edge ring electrode 111 to compensate for any edgering erosion. The increased RF voltage or current at the edge ring 106adjusts the location of the plasma sheath 260 to correct for any erosionof the edge ring 106.

In some aspects, to control extreme edge plasma parameters, the RFvoltage at the edge ring 106 may be adjusted to be greater than or lessthan the RF voltage of the substrate 105.

FIGS. 7A and 7B are schematic circuit diagrams illustrating anotherembodiment of a RF circuit 700. The RF circuit 700 includes thecapacitance elements C1, C2, C3, C4, C7, C8 and C9, which are describedin the above embodiment illustrated in FIGS. 4A and 4B, thusdescriptions thereof are omitted.

The RF circuit 700 includes a parallel LC resonant circuit that iscoupled to the RF power source 110 and to the edge ring electrode 111through one or more transmission lines 141. The parallel LC resonantcircuit includes variable capacitor C5 720 and inductor L 730, bothcoupled to the RF power source 110 and to the edge ring electrode 111.The parallel LC resonant circuit can be tuned to manipulate theamplitude and phase of voltage or current applied to the edge ringelectrode 111 by adjusting the variable capacitance C5 720.

In some embodiments, voltages (e.g., V1, V2), currents (e.g., I1, I2),and their phases (e.g., ϕv1, ϕv2, ϕi1, ϕi2) can be measured at the edgering electrode 111 and the baseplate 405, respectively. Using themeasured voltages, currents, and their phases at these points, thecontroller 108 monitors a voltage ratio of edge ring 106 and substrate105 and a phase difference between the voltages of the edge ring 106 andthe substrate 105. Additionally or alternatively, the controller 108monitors an amplitude current ratio and phase difference between edgering 106 and substrate 105.

As described in the above embodiments, based on the monitoring results,the parallel LC resonant circuit can manipulate the voltage or currentat the edge ring 106 to adjust the location of the plasma sheath 260 tocorrect for the erosion of the edge ring 106 or to control the extremeedge plasma parameters. The total RF power input can be also adjusted inorder to keep the voltage of the substrate 105 constant for minimalprocess impact on the center of the substrate 105.

FIGS. 8A and 8B are schematic circuit diagrams illustrating anotherembodiment of a RF circuit 800. The RF model 800 includes thecapacitance elements C1, C2, C3, C4, C7, C8 and C9, which are describedin the above embodiment illustrated in FIGS. 4A and 4B, thusdescriptions thereof are omitted.

The RF circuit model 800 includes a series LC resonant circuit that iscoupled to the RF power source 110 and to the edge ring electrode 111through one or more transmission lines 141. The serial LC resonantcircuit includes variable capacitor C5 820 and inductor L 830 connectedin series to the capacitance C5 820. In addition, a variable capacitorC6 840 is coupled to ground and to a point between the inductor L 830and the variable capacitor C5 820.

In some embodiments, voltages (e.g., V1, V2, V3), currents (e.g., I1,I2, I3), and their phases (e.g., ϕv1, ϕv2, ϕv3, ϕi1, ϕi2, ϕi3) can bemeasured at the edge ring electrode 111, the baseplate 405, and a pointbetween the inductor and capacitor(s), respectively. Using the measuredvoltages, currents, and their phases at these points, the controller 108monitors a voltage ratio of edge ring 106 and substrate 105 and a phasedifference between the voltages of the edge ring 106 and the substrate105. Additionally or alternatively, the controller 108 monitors acurrent amplitude ratio and phase difference between edge ring 106 andsubstrate 105. The total RF power input can be also adjusted in order tokeep the voltage of the substrate 105 constant for minimal processimpact on the center of the substrate 105.

Based on the monitoring results, the controller 108 determines whetherto tune the variable capacitors C5 820 and C6 840 to manipulate thevoltage or current developed at the edge ring 106 through the edge ringelectrode 111, such that the profile of the plasma sheath 260 results intarget processing of the substrate 105, particular near theradially-outward edge of the substrate 105.

FIGS. 9A and 9B are schematic circuit diagrams illustrating anotherembodiment of a RF circuit 900. The RF circuit 900 includes capacitanceelements C2, C3, C4, C7, and C9, which are described in the aboveembodiment illustrated in FIGS. 4A and also includes a capacitanceelement C1 between the substrate electrode 109 and the baseplate 405.Capacitance element C8 is between the substrate electrode 109 andsubstrate 105. The RF power source 110 is coupled to and supplies powerto a substrate 105 through a substrate electrode 109 or baseplate 405.This substrate electrode 109 may exist under the substrate 105 in the RFcircuits of the other embodiments provided in this disclosure.

The RF circuit 900 includes a serial LC resonant circuit that is coupledto the RF power source 110 and to the edge ring electrode 111 throughone or more transmission lines. The serial LC resonant circuit includesa variable capacitor C5 920 coupled to the RF power source 110, and aninductor L 930 coupled to the edge ring electrode 111 and connected inseries to the variable C5 920. The RF power source 110 also providespower to the substrate electrode 109 or baseplate 405.

In some embodiments, voltages (e.g., V1, V2, V3), currents (e.g., I1,I2, I3), and their phases (e.g., ϕv1, ϕv2, ϕv3, ϕi1, ϕi2, ϕi3) can bemeasured at the edge ring electrode 111, the substrate electrode 109 orbaseplate 405, and a point between the inductor 930 and the capacitor920, respectively. Using the measured voltages, currents, and theirphases at these points, the controller 108 monitors a voltage ratio ofedge ring 106 and substrate and a phase difference between the voltagesof the edge ring 106 and the substrate 105. Additionally oralternatively, the controller 108 monitors a current amplitude ratio andphase difference between edge ring 106 and substrate 105.

Based on the monitoring results, the serial LC resonant circuit can betuned to manipulate the amplitude and phase of voltage or currentapplied to the edge ring electrode 111. The total RF power input can bealso adjusted in order to keep the voltage of the substrate 105 constantfor minimal process impact on the center of the substrate 105.

FIGS. 10A and 10B are schematic circuit diagrams illustrating anotherembodiment of a RF circuit 1000. The RF circuit 1000 includescapacitance elements C2, C3, C4, C7, and C9, which are described in theabove embodiment illustrated in FIGS. 4A and 4B, thus descriptionsthereof are omitted. Also, the RF power source 110 is coupled andsupplies power to a substrate 105 through a substrate electrode 109 orbaseplate 405. A capacitance element C1 is present between the substrateelectrode 109 and the baseplate 405. Capacitance element C8 is betweenthe substrate electrode 109 and substrate 105.

The RF circuit 1000 includes a serial LC resonant circuit coupled to theRF power source 110 and to the edge ring electrode 111 through one ormore transmission lines 141. The serial LC resonant circuit includes avariable capacitor C5 1020 coupled to the RF power source 110, and aninductor L 1030 coupled to the variable capacitor C5 1020 in series andto the edge ring electrode 111. In addition, a variable capacitor C61040 is coupled to the ground and to a point between the variablecapacitor C5 1020 and inductor L 1030. Variable capacitor C6 1040 canalso be adjusted to a resonant condition with inductor 1030.

In some embodiments, voltages (e.g., V1, V2, V3), currents (e.g., I1,I2, I3), and their phases (e.g., ϕv1, ϕv2, ϕv3, ϕi1, ϕi2, ϕi3) can bemeasured at the edge ring electrode 111, the baseplate 405, and a pointbetween the inductor 1030 and the capacitor 1040, respectively. Usingthe measured voltages, currents, and their phases at these points, thecontroller 108 monitors a voltage ratio of edge ring and substrate and aphase difference between the voltages of the edge ring 106 and thesubstrate 105. Additionally or alternatively, the controller 108monitors a current amplitude ratio and phase difference between edgering 106 and substrate 105.

Based on the monitoring results, the variable capacitors C5 1020 and C61040 can be tuned to manipulate the amplitude and phase of voltage orcurrent applied to the edge ring electrode 111. The total RF power inputcan be also adjusted in order to keep the voltage of the substrate 105constant for minimal process impact on the center of the substrate 105.

In the embodiments described above, the tuning circuit 155 may include acapacitive circuit, an LC parallel resonant circuit, or LC serialresonant circuit as illustrated in FIGS. 4A through 10B, in which avariable capacitor C is coupled to the edge ring electrode 111. Theresonant frequency of the LC parallel resonant circuit or LC serialresonant circuit can be substantially close to the operating frequency,which enables a large variation of RF amplitude that is much larger andmuch smaller than the variation of RF amplitude of the substrate 105.

In another embodiment, the tuning circuit 155 can include two LCparallel resonant circuits or two LC serial resonant circuits asillustrated in FIGS. 11 through 15, in which two variable capacitors aswell as two inductors are coupled to the edge ring electrode 111. Thisenables a wide tuning range of edge ring RF voltage and current at twodifferent frequencies.

FIGS. 11A and 11B are schematic circuit diagrams illustrating anotherembodiment of a RF circuit 1100. The RF circuit 1100 may be a portion ofthe tuning circuit 155 shown in FIG. 1. To facilitate explanation, FIGS.11B illustrates the RF circuit 1100 overlaid on a partial view of thesubstrate support assembly 104. The RF circuit 1100 describes thefunctional relationships among components of a system.

In the RF circuit 1100, a capacitance element C1 is present between abaseplate 405 and the edge ring 106. A capacitance element C2 is presentbetween the edge ring 106 and the plasma 116 in the plasma sheath 260. Acapacitance element C3 is a capacitance between the edge ring 106 andthe edge ring electrode 111. A capacitance element C4 is disposedbetween the edge ring electrode 111 and the baseplate 405. A capacitanceelement C7 is present between the substrate 105 and the plasma 116within the plasma sheath 260. A capacitance element C8 is a capacitancebetween the substrate 105 and the baseplate 405. A capacitance elementC9 is disposed between the baseplate 405 and ground potential.Capacitance elements C2, C3, C4 and C9 correspond to an edge capacitancecircuit 408A. Capacitance elements C7 and C8 correspond to a centralcapacitance circuit 408B.

In one embodiment, the baseplate 405 corresponds to the facilities plate210 (shown in FIGS. 2A and 2B). In another embodiment, a bond layer 410can correspond to the heater 245 (shown in FIGS. 2A and 2B).

In this embodiment, a first variable capacitor 415 is coupled to the RFpower source 110 and to the edge ring electrode 111 through one or moretransmission lines 265, providing a path for power to the edge ringelectrode 111. Additionally, a first inductor 420 is provided betweenthe first variable capacitor 415 and the edge ring electrode 111, andone pole (a first pole) of a second inductor 425 is coupled to a signalline 430 between the first variable capacitor 415 and the first inductor420. A second pole of the second inductor 425 is coupled to the centralcapacitance circuit 408B. The second inductor 425 may by-pass the firstvariable capacitor 415. Further, a second variable capacitor 435 iscoupled between ground potential and the signal line 430. Thearrangement of the first variable capacitor 415 and the second inductor425 comprises a parallel LC circuit between the baseplate 405 and theedge ring electrode 111.

When the power is applied to the edge ring electrode 111, RF voltage andcurrent develop at the edge ring 106 as a result of coupling. The secondinductor 425 enables tuning of high and low voltages at the edge ringelectrode 111 at two different frequencies (e.g., 13.56 MHz and 2 MHz).For example, the second inductor 425 enables adjustment of one frequencyfrom the RF power source 110 to the edge ring electrode 111 whether itis a frequency of 13.56 MHz or 2 MHz. Further, varying capacitance atthe first variable capacitor 415 and/or the second variable capacitor435 enables voltage adjustment at the edge ring electrode 111 in eitherof the two frequencies provided to the edge ring electrode 111 from theRF power source 110. For example, the voltage applied to the edge ringelectrode 111 can be varied from zero to two times the voltage appliedto the first electrode 109 at either of the two frequencies provided bythe RF power source 110 and/or the second RF power source 170.

In some embodiments, voltages (e.g., V1, V2), currents (e.g., I1, I2),and their phases (e.g., ϕv1, ϕv2, ϕi1, ϕi2) can be measured at the edgering electrode 111 and the baseplate 405. Using the measured voltages,currents, and their phases at these points, the controller 108 (FIG. 1)monitors a voltage ratio of edge ring 106 and the substrate 105, and aphase difference between the voltages of the edge ring 106 and thesubstrate 105. Additionally or alternatively, the controller 108monitors a current amplitude ratio and phase difference between the edgering 106 and the substrate 105.

Based on the monitoring results, one or a combination of the firstvariable capacitor 415 and the second variable capacitor 435 can beadjusted to manipulate voltage or current applied to the edge ringelectrode 111, which affects the voltage or current developed at theedge ring 106. Consequently, the height of the plasma sheath 260 abovethe edge ring 106 can be controlled.

FIGS. 12A and 12B are schematic circuit diagrams illustrating anotherembodiment of a RF circuit 1200. The RF circuit 1200 may be a portion ofthe tuning circuit 155 shown in FIG. 1. To facilitate explanation, FIG.12B illustrates the RF circuit 1200 overlaid on a partial view of thesubstrate support assembly 104. The RF circuit 1200 describes thefunctional relationships among components of a system.

The RF circuit 1200 is similar to the RF circuit 1100 with the followingexceptions. A first parallel LC circuit 505 is provided between groundpotential and the edge ring electrode 111. The first parallel LC circuit505 comprises the first inductor 420 and the second variable capacitor435 coupled to the signal line 430. Additionally, a second parallel LCcircuit 510 is provided between the baseplate 405 and the edge ringelectrode 111. When the parallel resonant circuits 505, 510 areresonant, the edge ring electrode 111 has a high impedance to ground orto the RF power source 110.

FIGS. 13A and 13B are schematic circuit diagrams illustrating anotherembodiment of a RF circuit 1000. The RF circuit 1300 may be a portion ofthe tuning circuit 155 shown in FIG. 1. To facilitate explanation, FIG.13B illustrates the RF circuit 1300 overlaid on a partial view of thesubstrate support assembly 104. The RF circuit 1300 describes thefunctional relationships among components of a system.

The RF circuit 1300 is similar to the RF circuits 1100 and/or 1200 withthe following exceptions. A series LC circuit 605 is provided betweenground potential and the edge ring electrode 111. The series LC circuit605 comprises the first inductor 420 and the second variable capacitor435 coupled to the signal line 430. Additionally, the second parallel LCcircuit 510 is provided between the baseplate 405 and the edge ringelectrode 111. The series resonant circuit 605 reduces the voltage onthe edge ring electrode 111 when resonant, while the parallel resonantcircuit 510 varies the coupling to the RF power source 110.

FIG. 14A and 14B are schematic circuit diagrams illustrating anotherembodiment of a RF circuit 1400. The RF circuit 1400 may be a portion ofthe tuning circuit 155 shown in FIG. 1. To facilitate explanation, FIG.14B illustrates the RF circuit 1400 overlaid on a partial view of thesubstrate support assembly 104. The RF circuit 1400 describes thefunctional relationships among components of a system.

The RF circuit 1400 is similar to the RF circuits 1100, 1200 and/or 1300with the following exceptions. A series LC circuit 705 is providedbetween the baseplate 405 and the edge ring electrode 111. The series LCcircuit 705 comprises the second inductor 425 and the first variablecapacitor 415 coupled to the signal line 430. Additionally, the firstparallel LC circuit 505 is provided between ground potential and theedge ring electrode 111. The series resonant circuit 705 can provide alow impedance to the RF power source 110, while the parallel resonantcircuit 505 can provide a high impedance to ground.

FIG. 15A and 15B are schematic circuit diagrams illustrating anotherembodiment of a RF circuit 1000. The RF circuit 1500 may be a portion ofthe tuning circuit 155 shown in FIG. 1. To facilitate explanation, FIG.15B illustrates the RF circuit 1500 overlaid on a partial view of thesubstrate support assembly 104. The RF circuit 1500 describes thefunctional relationships among components of a system.

The RF circuit 1500 is similar to the RF circuits 1100, 1200, 1300and/or 1400 with the following exceptions. The series LC circuit 605comprises a first LC circuit that is combined with the series LC circuit705 as a second series LC circuit 605. Both of the series LC circuit 605and the series LC circuit 705 are described in FIGS. 13A-14B. The firstseries resonant circuit 705 can provide a low impedance to the RF powersource 110, while the second series resonant circuit 605 can provide ahigh impedance to ground.

When the power is applied to the ring electrode 111, RF voltage andcurrent develop at the edge ring 106 as a result of coupling. The twoinductors 420 and 425 have fixed values. Tuning the two variablecapacitors 415 and 435 in different range of values enables tuning ofhigh and low voltages at the ring electrode 111 at two differentfrequencies (e.g., 13.56 MHz and 2 MHz). For example, varyingcapacitance at the first variable capacitor 415 and/or the secondvariable capacitor 435 enables voltage adjustment at the ring electrode111 in either of the two frequencies provided to the ring electrode 111from the RF power source 110 and/or the second RF power source 170. Forexample, the voltage applied to the ring electrode 111 can be variedfrom zero to two times the voltage applied to the first electrode 109 ateither of the two frequencies provided by the RF power source 110 and/orthe second RF power source 170.

In some embodiments, voltages, currents, and their phases can bemeasured at the ring electrode 111 and the baseplate 405. Using themeasured voltages, currents, and their phases at these points, thesystem controller 108 (FIG. 1) monitors a voltage ratio of edge ring 106and the substrate 105, and a phase difference between the voltages ofthe edge ring 106 and the substrate 105. Additionally or alternatively,the system controller 108 monitors the ratio of current amplitude andphase difference between the edge ring 106 and the substrate 105.

Based on the monitoring results, one or a combination of the firstvariable capacitor 415 and the second variable capacitor 435 can beadjusted to manipulate voltage or current applied to the ring electrode111, which affects the voltage or current developed at the edge ring106. Consequently, the height of the plasma sheath 260 above the edgering 106 can be controlled.

FIG. 16 is a schematic side view illustrating a portion of a substratesupport assembly 1600 having a quartz cover ring 907 disposed on theedge ring 106. The substrate support assembly 1600 and the quartz coverring 907 may be utilized as the substrate support assembly 104 of FIGS.1-2B.

The quartz cover ring 907 may be utilized when particle generation is anissue. For example, in logic circuit applications, where particles mustbe kept at a minimum, the quartz cover ring 907 may be used to preventetching of the edge ring 106 which may produce particles. The quartzcover ring 907 has a width dimension 910 that is substantially equal toa width dimension of the edge ring 106. The quartz cover ring 907 has athickness 915 that is about 0.03 inches to about 0.09 inches, forexample, about 0.06 inches.

Testing of the substrate support assembly 104 having the various RFcircuits 400-1500 shows enhanced plasma control at the edge of asubstrate. Further, feature tilting control is enhanced. For example,tests with a 300 mm substrate indicate that low voltages and highvoltages applied to the edge ring electrode 111 below the edge ring 106has been shown to produce a range of greater than about 7 degrees at aradius 146 mm, or greater. Additionally, testing of a substrate supportassembly 104 with the quartz cover ring 907 yielded results similar totests of the substrate support assembly 104 without the quartz coverring 907. Thus, utilizing the quartz cover ring 907 provides plasmasheath control as well as reducing particle generation.

FIG. 17 is a flow diagram illustrating an operation process 1700 for theRF circuits described above according to one aspect of the disclosure.This operation process can apply generally to the RF circuitconfigurations of FIGS. 4A-15B provided in this disclosure.

In operation 1705, the controller 108 calibrates an RF circuit to findthe relation between the voltages of the substrate 105 and the substrateelectrode 109 (or the baseplate 405).

In operation 1710, the controller 108 calibrates the RF circuit to findthe relation between the voltages of the edge ring 106 and the edge ringelectrode 111.

In operation 1715, voltages, currents, and their phases are measured atthe edge ring electrode, the substrate electrode 109 (or baseplate), anda point between the inductor and the capacitor, respectively. Based onthe measured results, the controller 108 monitors an amplitude ratio andphase difference between the voltages of the edge ring 106 and thesubstrate 105 by monitoring a voltage ratio and phase difference betweenthe voltages of edge ring electrode 111 and substrate electrode 109 (or,in some embodiments, the baseplate 405).

In operation 1720, the controller 108 calculates the voltage of thesubstrate 105 based on the (V, I, phase) at the baseplate 405 (or thesubstrate electrode 109).

In operation 1725, the controller 108 operates a feedback loop to adjustthe RF power source 110 such that the substrate electrode 109 (orbaseplate 405) maintains constant the amplitude of voltage at thesubstrate at a certain level so that the plasma parameters at the centerof the substrate 105 keeps constant while the parameters at the extremeedge is changed by adjusting the variable capacitor C5 and/or C6.

In operation 1730, the controller 108 calculates the voltage of the edgering 106 based on the (V, I, phase) at the edge ring electrode 111.

In operation 1735, the controller 108 operates a feedback loop to tunethe variable capacitor C5 and/or C6 to obtain a target amplitude of thevoltage at the edge ring 106 as necessary to maintain a targeted edgering to substrate voltage ratio in order to compensate for any erosionof the edge ring 106 or adjust the process profile on substrate edge.

Subsequently, the controller proceeds to operation 1715 to monitor avoltage ratio and a phase difference between the voltages of the edgering 106 and the substrate while substrates continue to be processed.

FIG. 18 is a flow diagram illustrating an operation process 1800 for theRF circuits according to another aspect of the disclosure. Thisoperation process can apply generally to the RF circuit configurationsof FIGS. 4A-15B provided in this disclosure.

In operation 1805, the controller 108 calibrates an RF circuit to find acondition for a minimal or zero voltage at the edge ring 106.

In operation 1810, under the conditions for a minimal or zero voltage atthe edge ring, the controller 108 measures an RF current going to thesubstrate 105.

In operation 1815, the controller 108 calculates the voltage of thesubstrate 105 based on the (V, I, phase) at the baseplate 405 (or thesubstrate electrode 109).

In operation 1820, the controller 108 operates a feedback loop to adjustthe RF power source 110 to maintain the substrate electrode 109 (orbaseplate 405) at a certain amplitude of voltage so that the plasmaparameters at the center of the substrate keeps constant.

In operation 1825, voltages, currents, and their phases are measured atthe edge ring electrode 111, the substrate electrode 109 (or baseplate405), and a point between the inductor and the capacitor, respectively.Based on the measured results, the controller 108 monitors amplitudesand phases of the total current generated from the RF power source 110and the current going to the ground, so that the amplitude and phase ofthe current going to the edge ring electrode 111 can be calculated,e.g., by subtracting the current going to the ground from the totalcurrent.

In operation 1830, the controller 108 calculates the edge ring tosubstrate RF current ratio based on the (V, I, phase) measurements atthe edge ring electrode 111 and baseplate 405 (or substrate electrode109).

In operation 1835, the controller 108 operates a feedback loop to tunethe variable capacitor C5 and/or C6 to obtain a target amplitude andphase of the current at the edge ring 106 as needed in order to achieveand maintain the targeted edge ring to substrate RF current ratio inorder to compensate for any erosion of the edge ring 106 or adjust theprocess profile on substrate edge.

Subsequently, the controller 108 proceeds to operation 1830 to monitoran amplitude and phase of current generated from the RF power source 110and current going to the ground while substrates continue to beprocessed.

For processes with two different frequencies of RF bias input 110, theuser can choose to tune the edge ring RF voltage and current at eitherfrequency (e.g. 2 or 13 MHz), then different ranges of the variablecapacitance C5 can be used for the tuning with the assistance of thefeedback control loop 1700 or 1800.

FIGS. 19A to 19D depict example simulation results of the amplituderatio and the phase difference between the edge ring electrode 111 andthe substrate electrode 109 when employing each of the RF circuitsdisclosed in the disclosure.

FIG. 19A shows that the embodiments provided in this disclosure allowfor manipulating the voltage ratio between the edge ring electrode 111and the substrate electrode 109 from 0.2 to 3.2 by adjusting a variablecapacitance, e.g., C5 from 20 pF to 250 pF. Also, as shown in FIG. 19Bthe embodiments provided in this disclosure are able to manipulate thephase difference between the edge ring electrode and the substrateelectrode 109 from 0 to 110 degrees by adjusting a variable capacitance,e.g., C5 from 20 pF to 250 pF. The simulation result of FIGS. 19A and19B can be generated when employing the RF circuits of, for example,FIGS. 6A and 6B or FIGS. 7A and 7B.

FIG. 19C shows that the embodiments in this disclosure allow formanipulating the voltage ratio between the edge ring electrode 111 andthe substrate electrode 109 from 0.4 to 4.1 by adjusting a variablecapacitance, e.g., C5 from 20 pF to 250 pF. Also, FIG. 19D shows thatthe embodiments can manipulate the phase difference between the edgering electrode 111 and the substrate electrode 109 from 0 to −170degrees by adjusting a variable capacitance, e.g., C5 from 20 pF to 250pF. The simulation result of FIGS. 19A and 19B can be generated whenemploying the RF circuits of, for example, FIGS. 8A and 8B.

As shown in the above simulation results, the RF circuits described inthis disclosure are able to manipulate the amplitude and phase of thevoltage or current of the edge ring 106 relative to those of thesubstrate 105 across a wide range, which allows for maintaining theheight of the plasma sheath above the edge ring 106 to a certain levelas desired.

Benefits of the disclosure include the ability to adjust plasma sheathsat the substrate edge in lieu of replacing chamber components, therebyimproving device yield while mitigating downtime and reducingexpenditures on consumables. Additionally, aspects described hereinallow for the plasma sheath to be adjusted at the substrate edge withoutaffecting the plasma parameters at substrate center, thereby providing atuning knob for extreme edge process profile control and feature tiltingcorrection.

What is claimed is:
 1. A substrate support, comprising: a vertical stackcomprising: an electrostatic chuck having a substrate electrode embeddedtherein for chucking a substrate to an upper surface of theelectrostatic chuck, wherein the electrostatic chuck includes one ormore channels through which a fluid is provided to facilitatetemperature control of the substrate support, a ground plate surroundingan insulating layer, wherein the insulating layer is below theelectrostatic chuck, a baseplate underneath the electrostatic chuck tofeed radio frequency (RF) power to the substrate, the baseplatepositioned between a lower portion of the ground plate and theelectrostatic chuck, a quartz pipe ring circumscribing the baseplate andthe electrostatic chuck; an edge ring disposed over the electrostaticchuck and circumscribes the substrate; an edge ring electrode locatedunderneath the edge ring; and a tuning circuit configured to couple afirst RF power source at a first frequency and a second RF power sourceat a second frequency that provide power to the substrate electrode andto the edge ring electrode through three transmission lines spaced aboutthe substrate support at even intervals, the tuning circuit comprising:a RF circuit including a LC resonant circuit coupled to the edge ringelectrode through one of the transmission lines, the LC resonant circuitcomprising: a first variable capacitor coupled to the edge ringelectrode, and a first inductor coupled to the edge ring electrode. 2.The substrate support of claim 1, further comprising: a controllerconfigured to adjust the first variable capacitor to manipulate eithervoltage o current at the edge ring through the edge ring electrode. 3.The substrate support of claim 1, wherein the first variable capacitoris coupled to one of the RF power sources, and the RF circuit furtherincludes a second variable capacitor that is coupled to the ground andto a point between the edge ring electrode and the first variablecapacitor.
 4. The substrate support of claim 3, wherein a first range ofvalues of the combination of the first variable capacitor and the secondvariable capacitor increase/decrease amplitude of voltage at the edgering at one frequency, and wherein a second range of the combination ofthe first variable capacitor and the second variable capacitorincrease/decrease the amplitude of the voltage at the edge ring atanother frequency.
 5. The substrate support of claim 1, wherein the RFcircuit further comprises the first inductor coupled to the firstvariable capacitor.
 6. The substrate support of claim 5, wherein thefirst variable capacitor is coupled to ground, wherein the firstinductor is connected between the first variable capacitor and the edgering electrode.
 7. The substrate support of claim 5, wherein the firstvariable capacitor is coupled to ground, wherein the first inductor andthe first variable capacitor are connected in series.
 8. The substratesupport of claim 5, wherein the first variable capacitor is coupled toground, wherein the first inductor and the first variable capacitor areconnected in parallel.
 9. The substrate support of claim 5, wherein theRF circuit further comprises a second variable capacitor connected to asecond inductor.
 10. The substrate support of claim 9, wherein thesecond variable capacitor and the second inductor are connected to theedge ring electrode between an RF power source and the first inductorand the first variable capacitor.
 11. A process chamber comprising: achamber body; a lid disposed on the chamber body; an inductively coupledplasma apparatus positioned above the lid; and a substrate supportpositioned within the chamber body, the substrate support comprising: avertical stack comprising: an electrostatic chuck having a substrateelectrode embedded therein for chucking a substrate to an upper surfaceof the electrostatic chuck, wherein the electrostatic chuck includes oneor more channels through which a fluid is provided to facilitatetemperature control of the substrate support, a ground plate surroundingan insulating layer, wherein the insulating layer is below theelectrostatic chuck, a baseplate underneath the electrostatic chuck tofeed radio frequency (RF) power to the substrate, the baseplatepositioned between a lower portion of the ground plate and theelectrostatic chuck, a quartz pipe ring circumscribing the baseplate andthe electrostatic chuck; an edge ring disposed over the electrostaticchuck and circumscribes the substrate an edge ring electrode locatedabout a periphery of the baseplate, wherein the edge ring electrode islocated underneath the edge ring: and a tuning circuit configured tocouple a first RF power source at a first frequency and a second RFpower source at a second frequency that provide power to the substrateelectrode and to the edge ring electrode through three transmissionlines spaced about the substrate support at even intevals, the tuningcircuit comprising: a RF circuit including: a LC resonant circuitcoupled to the edge ring electrode through one of the transmissionlines, the LC resonant circuit comprising: a first variable capacitor, afirst inductor, and a second inductor coupled to the edge ringelectrode.
 12. The process chamber of claim 11, further comprising: acontroller configured to adjust the first variable capacitor tomanipulate either voltage or current at the edge ring through the edgering electrode, wherein the first variable capacitor is coupled to oneof the RF power sources, and the RF circuit further includes a secondvariable capacitor that is coupled to ground and to a point between theedge ring electrode and the first variable capacitor.
 13. The processchamber of claim 11, wherein the first variable capacitor is coupled toground, and the first inductor is coupled to ground and to the edge ringelectrode, and is connected in parallel to the first variable capacitor.14. The process chamber of claim 11, wherein the first variablecapacitor is coupled to ground, and the first inductor is coupled toground and to the edge ring electrode, and is connected in series to thefirst variable capacitor.
 15. The substrate support of claim 11, whereinthe first variable capacitor is coupled to ground, and the firstinductor and the first variable capacitor are connected in series. 16.The substrate support of claim 11, wherein the first variable capacitoris coupled to ground, and the first inductor and the first variablecapacitor are connected in parallel.
 17. The process chamber of claim11, herein the second inductor is coupled to one of the RF power sourcesand to the edge ring electrode, and wherein the first variable capacitoris coupled to the RE power source and to the edge ring electrode, and isconnected in parallel to the first inductor.